High Energy Physics

"International researchers at the Large Hadron Collider (LHC), in Geneva, Switzerland, will soon embark on one of science's greatest adventures. With its very high energy, previously seen only in cosmic rays, the particle collider will probe the inner structure of matter at distances ten times smaller than any previous experiments. The LHC will address many of the mysteries surrounding the smallest particles of matter. It may also pierce secrets that the Universe has hidden since the early stages of the Big Bang, such as the nature of dark matter and the origin of matter itself. This will be the largest scientific experiment ever attempted and the complex international efforts to bring the 27km-long machine to life, including Canada’s involvement, will also be explained."

About John EllisBorn in London on July 1st, 1946, Ellis grew up in Potters Bar, a suburb that some Londoners used to regard as the northern boundary of civilization. It was there, at around the age of 12, he decided to become a physicist – largely due to the interesting science books he read at the local library. Ellis obtained his BA and PHD from Cambridge University where he studied mathematics and theoretical physics. Following a year at the Stanford Linear Accelerator Center and an additional year at the California Institute of Technology as a research associate, Ellis joined CERN in 1973 and became leader of the Theory Division for six years. Currently, he is a senior staff member. Ellis is also an advisor on CERN’s relations with non-Member States.Ellis has published over 700 scientific articles in particle physics and related areas of cosmology and astrophysics. His research interests include the possible experimental consequences and tests of new theoretical ideas such as gauge theories of strong and electroweak interactions, grand unified theories, supersymmetry, and string theory. He was elected a Fellow of the Royal Society in 1985, and was awarded the Dirac Medal of the Institute of Physics in 2005. Ellis is also responsible for popularizing the term “Theory of Everything” in an article published in the journal Nature in 1986.

About Robert S. OrrProfessor Orr was born in Iran, and grew up in Scotland and South Wales. His father and uncles were all engineers in the ship building industry. His interest in physics was sparked early in his childhood by trying to make sense of his father’s textbooks. “Ever since I was a child, I took things apart to see how they worked” says Orr. “Doing that with matter is the ultimate challenge."

At present he is a Professor in the Department of Physics at the University of Toronto. He was NSERC Principal Investigator for ATLAS Canada from 1994 to 2007. ATLAS is a detector within the LHC at CERN. Orr earned his B.Sc. and Ph.D. at Imperial College, University of London, UK, and was a Post Doctoral Researcher at Rutherford Laboratory, also in the UK, as well as at the University of Wisconsin, Madison, USA. From 1974 to 1981 he was a CERN Fellow and Staff Physicist. He came to Canada in 1981 as an Institute of Particle Physics Research Scientist, and became a member of the faculty at the University of Toronto in 1989. Orr has worked at many of the world’s particle physics labs in the USA, Germany and Japan. He has a particular interest in the application of large scale computing clusters in this field, and in the development of new finds of detection devices.

If some form of string theory indeed describes the ultra high energy physics of our universe, then there are two ingredients which are very likely to remain at low energies. The first, is a fifth force in the form of an additional abelian gauge group. The second, and more dramatic, is supersymmetry. Both may be observed at the upcoming Large Hadron Collider. In this talk I will explore a possible intimate connection between these two ingredients which leads to surprising predictions.

I will present a construction of supersymmetric Wilson loop operators in N=4 SYM for an arbitrary path on an S3 subspace of space-time. I will show how they are evaluated in AdS and in particular that the string world-sheet is a generalized calibration with respect to an almost-complex structure associate to the supersymmetries preserved by the loop. I will present some special examples and in the case when the loop is restricted to an S2, some evidence that the calculation reduces to a perturbative calculation in YM in 2-dimensions on S2. This in turn is exactly soluble in terms of a 0-dimensional matrix model.

We present a general hydrodynamic theory of transport in the vicinity of superfluid-insulator transitions in two spatial dimensions described by ``Lorentz\'\'-invariant quantum critical points. We allow for a weak impurity scattering rate, a magnetic field $B$, and a deviation in the density, $rho$, from that of the insulator. We show that the frequency-dependent thermal and electric linear response functions, including the Nernst coefficient, are fully determined by a single transport coefficient (a universal electrical conductivity), the impurity scattering rate, and a few thermodynamic state variables. With reasonable estimates for the parameters, our results predict a magnetic field and temperature dependence of the Nernst signal which resembles measurements in the cuprates, including the overall magnitude. Our theory predicts a ``hydrodynamic cyclotron mode\'\' which could be observable in ultrapure samples. We also present exact results for the zero frequency transport co-efficients of a supersymmetric conformal field theory (CFT), which is solvable by the AdS/CFT correspondence. This correspondence maps the $rho$ and $B$ perturbations of the 2+1 dimensional CFT to electric and magnetic charges of a black hole in the 3+1 dimensional anti-de Sitter space. These exact results are found to be in full agreement with the general predictions of our hydrodynamic analysis in the appropriate limiting regime. The mapping of the hydrodynamic and AdS/CFT results under particle-vortex duality is also described.

Resent research seems to indicate that charged extremal black holes in D=4 supersymmetric theories should be most naturally described in terms of more primitive atomic constituents. I will briefly describe what I mean by these atomic constituents and how they appear to play a role in both BPS and non-BPS extremal black holes.